Most joysticks for computer games, and the like, are displacement-responsive in the sense that a hand-operated lever arm is manipulated, and this movement is sensed. However, another class of joysticks are “force-sensitive” insofar as the manually operated input moves imperceptivity, if at all. Such force-sensitive controllers are useful in a variety of applications, including games such as flight simulators, machine tools, cursor controls, vehicle controls, and other devices. In fact, certain ergonomic studies have shown that displacement-responsive joystick controllers give less positive control in some applications, and frequently suffer from excessive backlash as well as lack of tactile feedback in the area around the spring-loaded neutral position.
Based upon such advantages, various force-sensitive joystick designs have been developed for different purposes. As one example of many, U.S. Pat. No. 4,719,538 discloses a capacitive transducer having a plurality of first electrodes which, together with at least one second electrode, define a plurality of variable capacitors having capacitance variable with spacing. An actuator element responsive to externally applied force, and connected to a plate supporting at least one second electrode, angularly deflects the plate and at least one second electrode. This angular deflection, or “tilt,” causes the spacing of electrode sets disposed on opposite sides of the center of the plate to vary in a differential manner, thus causing the capacitances of the plurality of capacitors to vary in response to applied moment. Restoring force for the tiltable plate is provided by a flexible diaphragm connected to the plate. A transducer in which the differentially variable sets of capacitances determines the frequencies of a plurality of oscillators, and the differentially varying frequencies of the oscillators are combined to yield difference frequencies representative of the components of applied moment. A microprocessor device processes signals within the transducer and generates signals for controlling an external device.
However, although this design is said to be “force-responsive,” the flexible diaphragm results in considerable movement. In addition, the use of a flexible diaphragm may lead to wear and premature fatigue. Based upon the shortcomings of these and other devices, the need remains for an improved force-responsive joystick design that is substantially rigid and economical while offering long-term reliability.